During this period, the project team developed a series of high-throughput assays to examine differential toxicity between drug-nave cancer cell lines and P-gp-overexpressing drug-selected sublines. To identify P-gp substrates, high-throughput screens were performed against annotated libraries, which included a comprehensive collection of clinically approved drugs, probe small molecules with known mechanisms of action, and experimental therapeutics designed to modulate a wide range of targets.